Improvement and impairment in cognitive function after carotid endarterectomy: ¹²³I-iomazenil SPECT study

Abstract

While several studies have reported an improvement in cognition after carotid endarterectomy (CEA), others have demonstrated cognitive impairment associated with cerebral hyperperfusion. The mechanisms underlying these changes have remained unclear. Benzodiazepine receptor binding potential on ¹²³I iomazenil (IMZ) single photon emission computed tomography (SPECT) images correlates with brain neural density, and a reduction in cortical benzodiazepine receptor binding indicates cortical neural damage or loss. Recent IMZ-SPECT studies also suggest plasticity in the central benzodiazepine receptors and dynamic changes in the regulatory mechanisms of the neurotransmitter system. The purpose of our study was to determine the mechanisms leading to postoperative cognitive improvement and impairment using IMZ-SPECT. Postoperative hyperperfusion was significantly associated with postoperative hemispheric reduction of benzodiazepine receptor binding potential. Postoperative hyperperfusion and postoperative hemispheric reduction of benzodiazepine receptor binding potential were also significantly associated with postoperative cognitive impairment. Postoperative cognitive improvement was significantly associated with postoperative hemispheric increase in IMZ uptake when compared with postoperative increase in cerebral blood flow. In conclusion, cerebral hyperperfusion after CEA results in postoperative cortical neural loss that correlates with postoperative cognitive impairment, and cognitive improvement after CEA is related to the recovery of function of the neurotransmitter system in the cerebral cortex.